Ok dynoed my car on Wednesday just to test the new boost logging feature on the dyno, before I noticed my boost spiked to 23.8 psi and dropped down a lot on my autometer nexus gauges, Al suggested some time later that it could be a faulty gauge, so I changed it for a greddy like 5 months ago (not following Al's suggestion) but installed a Greddy 52mm. Noticed exactly the same thing, so here's the deal:

Spike 23.80 psi
7500 rpms 17 psi

The boost graph was horrid looked like a damn Roller Coaster with all the bumps, climbs, downhills etc.

Possible explanation:
Faulty Boost Controller? (Hallman Pro)
Dirty Air Filter? (Injen)
Wastegate Actuator Damaged? (stock)

If anyone has encounter a problem like this one, please some advice is well appreciated. my car made:

333 whp @ 7000 rpms @17 psi
324 tq. @4500 rpms @22 psi

I will find a way to scan the graph and post it here.
Thanks

 

Well one thing I've noticed is if your boost gauge flutters and reads high, you may have the 'T' installed backwards in the vacuum line (if not all 3 openings are symetrical). i.e. if there is one smaller opening, make sure that one goes to the boost gauge and not to one of the other 2 hose hookups.

 

If your boost is not constant, which given your description it isn't- you probably have a boost leak.

 

Do you have it hooked up through the diverter valve or off of the turbo nipple? I had the same problem running my MBC off the DV and switched it to the turbo outlet and the problem went away.

 

I would say the actuator is responsible for the taper - weak tension. It may also cause the pulsing too - exhaust pressures pushing on mbc pressure with a weak act spring in the middle.

 

hmm I will check on the actuator
and yes its connected directly to the turbo

 

Make sure it's not a leak first

 

I am willing to bet it will fail the leak test horribly :}

 

Maybe its a leak, who knows. I just know I need to fix it this week I got auto cross this weekend.

 

No leak!
Wastegate actuator adjusted, now holds 1.4 bar rock solid til 8k rpms

 

Wait what?! How did you adjust it? Are you using the stock actuator?

Please explain more thoroughly.

 

Wow, that's great. Did you do this yourself? If so, can you tell me how far you adjusted the turnbuckle (all the way?) and how much preload there is in terms of distance that you have to pull the arm to fit it on the pin?

I just took a peak at a buddies WGA due to him also having boost issues and the arm maybe needed 1mm of pull to get back on the pin ... although we didn't actually take the lower heatshield all the way off, so we didn't have room to adjust it yet ...

 

It is adjusted all the way, It was done at the shop that preps my car for Autocross.
Easier way is to remove the fan in the front, take the pin out of the turbo hotside that holds together the flapper outside arm and the actuator, unscrew both nuts that connect to the compressor housing, once outside turn that b%%ch til you see the actuator arm is looking a bit shorter once you do this you will notice the stock wasgate actuator has some markings, once its done the markings you wont be able to see them, that on the side that connects with the flapper outside arm.

The only *****y part is since the actuator arm is a bit shorter you will need to use some power in putting the nuts in the compressor, with your hand of course, it will be a bit difficult, but takes only minutes to do it.

Have fun

 

Thats some good info.

did you swap out your turbine housing @ any point or is it the oem unit?